Messages in this thread | | | Subject | Re: [PATCH] Use MTRRs by default for vesafb on x86-64 | From | (Eric W. Biederman) | Date | 16 May 2003 16:58:39 -0600 |
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Andi Kleen <ak@muc.de> writes:
> x86-64 cannot call the 32bit VESA BIOS. This means when vesafb is active > it does software copying in the vesa frame buffer. This is insanely slow > when the frame buffer is not marked for write combining. > > Some discussion showed that the use_mtrr flag was only off for some > old broken ET4000 ISA card. x86-64 has no ISA, so this is no concern. > Make the default depend on CONFIG_ISA. > > Patch for 2.5.69. Originally suggested by Gerd Knorr.
I don't know if this affects the frame buffers per se.
But often BIOS's on systems with large amounts of memory configure overlapping mtrrs (where an uncacheable mtrr would override a larger cacheable range). To date this has confused the linux mtrr code when it tries to modify things, and you cannot properly setup mtrrs. I believe this applies to both the fb case as well as X.
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